Telephone-exchange system.



C. L. GOODRUM.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED DEC-2.19m.

' Patented Sept. 10, 1918..

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ln van for: Char/es L. bod um.

UNITED STATES PATENT QFFIQE,

CHARLES L. GOODRUM, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed December 2, 1916.

To all whom it may concern:

Beit known that I, CHARLES L. GooDRUM, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Telephone- Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems, and more particularly to a system in which a calling subscriber can hold a connection which has been extended to a busy line but cannot establish a talking circuit thereto until said busy line becomes idle.

The object of the invention is to provide means for notifying a called subscriber, whose line has been found busy, that another subscriber is awaiting connection with his line.

The invention is illustrated in the accompanying drawing, which shows diagrammatically a connection between two subscribers, the circuits of a connector switch instrumental in extending such a connection being shown in detail.

In the drawing, the invention is shown associated with a two-wire automatic system, but it will be understood that it may be readily applied to any automatic or semiautomatic system.

In the present embodiment of the invention the called subscriber is notified of a waiting call by putting a tone on his line. It will, however, be seen that those skilled in the art may apply the principle of the invention to operate other notifying means.

In the system illustrated, when the calling subscriber removes his receiver from the hook, the line finder 1, shown diagrammatically, will be switched to his line terminals. T hereupon the subscriber manipulates the finger dial to operate the selector switch 2 in any desired manner to connect his line with the connector switch 15 in the bank of which are the terminals of the called line. When the subscribers line becomes connected through the selector, a circuit is completed from battery through the right-hand winding of the line relay LR, tip side of the line, subscribers substation, sleeve side of the line, left-hand winding of relay LR, to ground. The consequent energization of Specification of Letters Patent. Patented Sept. 10, 1918.

Serial No. 134,595.

the relay LR closes an energizing circuit for the slow relay 3, from ground, armature and front contact of relay LR, winding of relay 3. to battery. Relay 3, in pulling up, partially completes a circuit for energizing slow relay 4, which will be described later.

The subscriber now sends a second series of impulses, which causes the armature of the relay LR to vibrate. Each time that relay LR is deenergized a circuit is completed from ground, armature and back contact of relay LR, right-hand armature and front contact of relay 3, outermost arn'iature and contact of relay TR, side-switch arm 10 (position 1), through the winding of primary magnet PM, to battery and ground. The magnet PM responding to these impulses steps the wipers of the connector 15 to the group of terminals containing the terminals of the called subscriber.

A circuit for energizing relay 1 is completed in parallel with the circuit just traced from ground, armature and back contact of relay LR, armature and front contact of relay 3, through the winding of the relay 4. to battery. Relay 1 being slow to release remains energized during the sending of each series of impulses, and completes at its inner armature a circuit from ground, left-hand armature and contact of relay 3, inner armature and contact of relay 4:, sideswitch arm 9 (position 1), through the winding of the side-switch escape magnet Esc., to battery and ground. When the impulses have been sent, the consequent continned energization of the relay LR removes the circuit for holding up relay 4 long enough to allow it to fall back and allow the denergization of the escape magnet. The side switch, therefore, advances to the second position.

The subscriber now sends a third series of impulses, causing the energization of the relay 4, as has just been described, and operating through the second position of the side-switch arm 10 the secondary magnet SM of the connector switch. The magnet v over a circuit leading from ground at the fourth position of the side-switch arm such as 11' of some other line, bottom wiper of another connector such as 15, bottom Wiper of the calling connector 15, side-switch arm 11 (position 2), right-hand winding of the relay TR, to battery and ground. The relay TR will complete a locking circuit for itself from ground, left-hand winding of relay TR, innermost armature and contact of relay TR, through conducting portion of the constantly rotating disk 7, to battery and ground. The relay TR will complete a circuit for locking up the escape magnet Esc., from ground at its middle armature and contact, side-switch arm 9 (position 2), winding of escape magnet Esc., to battery and ground. This circuit prevents the advance of the side switch to the third, or ringing position, so long as relay TR is held up.

The purpose of the locking circuit through the left-hand winding of the relay TR is to prevent the connection of more than one calling line at a time ,to the called line when it becomes idle, for therelay TR can only be dei nergized when the called llne is idle snnultaneously with the passage of an insulated segment 19 of the disk 7 under the contact pen. As these insulated segments are circumferentially spaced on the various disks of a group of connectors so that no two will be under a contact pen at the same time, it is obvious that two lines cannot be so connected simultaneously.

When the relay TR becameenergized it also completed a circuit for energizing the relay 6 from ground, middle armature and contact of relay TR, side-switch arm 8 (position 2), outerarmature and contact of relay 1, through the winding of the relay 6, to battery and ground. The relay 6 in pulling up its armatures closed a circuit from the secondary coil of the transformer 18 through the condenser, left-hand armature and contact of relay 6, side-switch arm 13 (position 2), middle wiper of connector 15, tip side of the line, called subscribers substation, sleeve side of the line for wiper of connector 15, side-switch arm 14 (position 2), righthand armature and contact of relay 6, to the secondary cOil of transformer 18. .T his circuit, in connection with the tone generator and primary coil of transformer 18, places a tone on the called subscribers line apprising him of the fact that connection with his line is desired by another subscriber. As here provided, this tone will be continued either until the called subscriber completes his conversation, or until the calling subscriber abandons the call, in which case the restoration of the side switch of the connector will discontinue the tone. If desired the tone may beapplied intermittently by means of an interrupter.

A busy-back signal is also provided to the calling subscriber while the side switch is locked in the second position, the connection being made from ground, secondary of the transformer 17, side-switch arm 12 (position 2), off-normalcontact 0N condenser, tip side of the line, calling subscribers substation, sleeve side of the line and condenser through the winding of the retardation coil 16, to battery and ground.

Vvhen the called subscriber hangs up, the energizing circuit through the right-hand winding of the relay TR is broken by the restoration of the side-switch arm 11 of the connector switch which was formerly connected to his line. .The next time the insulated segment of thedisk 7 passes under the contact pen it will break the locking circuit through the left-hand winding of the relay TR,'which will thereupon become deenergized. The locking circuit for .the escape magnet is thereby broken at the, middle armature of the relay TR, and the escape magnet will, therefore, allow the advance of the side switch into itsthird position.

In this position of the side switch, the escape magnet will be again energized from ground, left-hand armature and contact of relay-3, armature and contact of slow relay 5, side-switch arm 9 (position 3), through the winding of the escape magnet, to battery and ground. The pulling up of the arma- (position 3), to ground. The resistance ofthe ringer is so high that relay 5, whichls 1 low wound, will not energize in series with it. Ringing will continue intermittently until the called subscriber removes his receiver, at which time the shunting of the ringer by his switchhook will reduce the resistance of the circuit sufficiently to allow the energization of the relay 5, which breaks at its armature the energizing circuit of magnet Esc. The magnet Esc. thereupon falls back, advancing the side switch to its fourth position.- In this position the talking circuit is complete between the calling and called subscriber, and talking current for the called subscriber is supplied through the retardation coil 16.

At the end of the conversation, when the calling subscriber hangs up his receiver he breaks at his switchhook the circuit for holding up the relay LR, which thereupon retracts its armature. In falling back the armature of the relay LR breaks the circuit of the relay 3, which thereupon falls back.

aaraseo A circuit is thus completed from ground, armature and back contact of the relay LR, armature and back contact of the relay 3, off-normal contact 0N through the winding of the release magnet RM, to battery and ground. This causes the restoration of the connector switch. The selector and linefinder will thereupon be restored in the wellknown manner.

What is claimed is:

1. In a telephone exchange system, the combination with lines leading from a central station to subscribers stations, automatic means for connecting a calling subscribers line to a wanted subscribers line, means for testing the idle or busy condition of a called subscribers line, and automatic means for notifying a called subscriber when busy that another connection with his line is desired.

2. In a telephone exchange system, the combination with lines leading from a central station to subscribers substations,means for connecting a calling subscribers line to a called subscribers line, means for testing the idle or busy condition of a called subscribers line, automatic means for notifying a called subscriber when busy, that another connection with his line is desired, means for preventing connection between a calling line and a busy called line, and means for establishing said connection when said called line becomes idle.

3. In a telephone exchange system, subscribers lines, means including an automatic connector switch for connecting a calling to a called subscribers line, a side switch associated with said connector switch, actuating means for said side switch, means for testing the idle or busy condition of a called subscribers line, means actuated when said subscribers line tests busy for preventing further movement of said-side switch during the extent of said busy condition, signalin means operated simultaneously with sai' preventing means, means at the called subscribers substation responsive to said signaling means for indicating that another connection is desired, and means for rendering ineffective said preventing means and comcombination with telephone lines, automatic switches for interconnecting said lines, means for testing the idle or busy condition of a called line, means for preventing the completion of a connection between a calling line and a busy called line, means for notifying a busy called subscriber that another connection to his line is desired, and means for rendering ineffective said notifying means whenever the waiting party abandons the call.

5. In a telephone exchange system, the combination with telephone lines, automatic switches for interconnecting said lines, means for testing the idle or busy condition of a called line, means for preventing the completion of a connection to a busy called line, means for producing a tone, and means for connecting said tone producing means to'a busy called line when additional connection with said line is desired.

6. In a telephone exchange system, the combination with telephone lines, automatic switches for interconnecting said lines, means for testing the idleor busy condition of a called line, means for preventing the completion of a connection to a busy called line, means for producing a tone, means for connecting said tone producing means to a busy called line when connection with said line is desired by an additional subscriber, and means for discontinuing said tone in case the additional subscriber abandons the call.

7. In a telephone exchange system, a busy line, a plurality of calling lines, means for placing a busy condition on the busy line, means for extending a connection from each calling line to said busy line, means responsive to said lousy condition for preventing the completion of the extended connections, means for producing characteristic signals, means responsive to said busy condition for connecting said signal producing means to the busy line, and means operative upon the busy line becoming idle to permit the completionof only one of said extended connections.

In witness whereof, I hereunto subscribe my name this 29th day of November A. D.,

CHARLES L. GOODRUM. 

